During pregnancy, the placenta serves as the link between mother and fetus, attaching to the uterine wall to provide oxygen and nutrients. After the baby is born, this organ typically detaches cleanly from the uterus. Placenta accreta is a condition where the placenta attaches too deeply into the uterine wall. In some instances, the placenta may invade the uterine muscles (placenta increta) or grow completely through the uterine wall (placenta percreta).
Causes and Risk Factors
Placenta accreta is linked to abnormalities in the uterine lining, often from scarring. The primary risk factor is a previous cesarean section (C-section), as scar tissue allows the placenta to implant more deeply. The risk increases with the number of C-sections a person has had.
Other types of uterine surgery that create scarring can also elevate the risk. These procedures include myomectomy for fibroid removal or endometrial ablation. A history of difficult placental deliveries in previous pregnancies can also be a contributing factor.
Certain conditions related to the pregnancy itself increase the risk of placenta accreta. If the placenta is positioned low in the uterus, either partially or completely covering the cervix—a condition known as placenta previa—the risk is higher. Advanced maternal age, specifically being over 35, and having had multiple pregnancies are also recognized risk factors.
Diagnosis During Pregnancy
Placenta accreta is often identified during routine prenatal appointments, as the condition does not cause noticeable physical symptoms. The most common diagnostic tool is an ultrasound. During the scan, a healthcare provider looks for specific signs, such as the absence of the normal clear space between the placenta and the uterine wall.
If an ultrasound suggests placenta accreta, a magnetic resonance imaging (MRI) scan may be ordered. An MRI offers a more detailed view of the pelvic organs to help determine the precise depth of placental invasion. This imaging helps confirm the diagnosis and assess if the placenta has grown into the uterine wall or is affecting nearby organs like the bladder. Early and accurate diagnosis is a main component of planning for a safe delivery and managing potential complications.
Maternal and Fetal Health Risks
For the mother, the primary risk associated with placenta accreta is severe hemorrhage (massive blood loss) at delivery. This happens because the placenta does not detach from the uterine wall as it should, and the attempt to remove it can lead to torrential bleeding. This blood loss can be life-threatening and may lead to complications such as kidney or lung failure. Up to 90% of patients require a blood transfusion.
To control this severe bleeding, a hysterectomy—the surgical removal of the uterus—is often necessary immediately following the C-section delivery. While this procedure can be life-saving, it results in the permanent loss of fertility, which can have long-term psychological impacts. There is also a risk of injury to adjacent organs during the surgery, particularly the bladder or ureters.
The condition does not directly harm the developing fetus. However, the primary risk to the baby stems from the need for a planned preterm delivery to minimize complications for the mother. Babies born prematurely, before 37 weeks of gestation, may face health challenges, such as respiratory problems or difficulty gaining weight, and may require care in a neonatal intensive care unit (NICU).
Specialized Delivery and Management
A diagnosis of placenta accreta requires a delivery plan from a specialized, multidisciplinary medical team. This team is typically led by a maternal-fetal medicine specialist and an experienced OB surgeon and includes an anesthesiologist, a urologist, and neonatal care providers. The goal is to ensure all aspects of the complex delivery are managed by experts.
The standard approach for managing placenta accreta is a planned cesarean delivery followed immediately by a hysterectomy. This procedure, known as a cesarean hysterectomy, is performed to prevent the catastrophic blood loss that would likely occur if there were an attempt to separate the placenta from the uterine wall. The delivery is electively scheduled, often between 34 and 37 weeks of pregnancy, to strike a balance between fetal maturity and the risk of an emergency delivery.
The choice of hospital is a significant part of the management plan. Deliveries for placenta accreta should take place at a well-equipped medical center, often a Level III or IV perinatal facility. These hospitals have the necessary resources, including an intensive care unit (ICU), an interventional radiology service, and a fully stocked blood bank, to handle the potential for massive hemorrhage and other surgical complications that may arise.